JP4412458B2 - Mixer circuit - Google Patents

Description

  The present invention relates to a mixer circuit suitable for use in a self-heterodyne communication type wireless communication apparatus.

  Generally, in a radio communication apparatus, frequency conversion from a signal processing IF (Intermediate Frequency) signal having a relatively low frequency to a transmission RF (Radio Frequency) signal having a relatively high frequency, or an RF signal to an IF signal A local oscillation signal (hereinafter referred to as an LO signal) is used for frequency conversion to.

  In a wireless communication device using a high frequency band such as a microwave or a millimeter wave band, the LO signal frequency is high, so that it is difficult to realize a local oscillation circuit that oscillates stably with low phase noise. It becomes a factor which raises the cost of a communication apparatus. Therefore, Non-Patent Document 1 proposes a self-heterodyne communication system that transmits an LO signal together with an RF signal from a transmission apparatus.

  FIG. 15 is a schematic diagram showing the configuration of the self-heterodyne communication method.

  As shown in FIG. 15, in the self-heterodyne communication method, the transmitter device 200 uses the LO signal to perform frequency conversion from the IF signal to the RF signal, and the power for amplifying the output signal of the mixer circuit 201 to the transmission power. The receiving apparatus 300 includes a detector that regenerates an IF signal from the transmitted RF signal and LO signal. In such a configuration, the local oscillation circuit for generating the LO signal is not necessary on the receiving apparatus 300 side, so that the receiving apparatus 300 can be reduced in size and cost.

  By the way, according to Non-Patent Document 2, in the self-heterodyne communication method, the transmission power of the RF signal and the LO signal are set to be approximately the same in order to increase the reception carrier power to noise power ratio under the condition that the transmission power is constant. It is desirable. Moreover, in the receiving device 300 of the self-heterodyne communication method, it is generally desirable that the power level of the received LO signal be as constant as possible.

  However, if the mixer circuit is configured with a simple single diode, the output power of the LO signal becomes larger than the RF signal. Therefore, in the self-heterodyne communication method, a balanced mixer circuit that can suppress the output power of the LO signal is used.

  As a small balance mixer circuit, for example, an even harmonic type mixer circuit having an anti-parallel diode portion in which two diodes are connected in parallel and in reverse polarity is known.

  FIG. 16 is a circuit diagram showing a configuration of a mixer circuit having a conventional anti-parallel diode section. FIG. 17 is a graph showing the characteristics of the mixer circuit shown in FIG. 16. FIG. 17A is a graph showing current-voltage characteristics, FIG. 17B is a waveform diagram showing output waveforms, and FIG. It is a graph which shows the frequency characteristic of an output signal.

  As shown in FIG. 16, the conventional mixer circuit includes an anti-parallel diode unit 101, a short stub 102 inserted between the input end of the anti-parallel diode unit 101 and the ground potential, and an output end of the anti-parallel diode unit 101. The open stub 103 has one end connected and the other end open.

  The input terminal of the anti-parallel diode unit 101 shown in FIG. 16 receives a frequency signal ½ of the IF signal and the LO signal (hereinafter referred to as LO / 2 signal), and the output terminal of the anti-parallel diode unit 101. Outputs an RF signal and an LO signal, respectively.

  The short stub 102 is formed with a length equal to the electrical length of 1/2 wavelength of the LO signal, for example, the connection point 104 is opened by the LO / 2 signal and shorted by the LO signal that is the second harmonic signal. . The open stub 103 has a length equal to the electrical length of a half wavelength of the LO signal, for example, the connection point 105 is short-circuited by the LO / 2 signal and opened by the LO signal that is the second harmonic signal. It is formed.

Since the conventional anti-parallel diode section 101 is composed of two diodes D101 and D102 having the same characteristics, as shown in FIG. 17A, the input voltage vs. output current characteristics symmetrical with respect to the origin 0 of the graph are obtained. As shown in FIG. 17B, a signal waveform having the same positive and negative maximum current values (I _max ) is output with respect to the sine wave signal input. At this time, the frequency components of the output signal are the frequency f0 of the input signal and its odd harmonics 3f0, 5f0,..., And the even harmonics 2f0, 4f0,. .

  When a LO / 2 signal and an IF signal are input to a mixer circuit having such characteristics, the mixer circuit frequency-mixes those signals.

の関係式を満たす信号を出力する。

A signal satisfying the relational expression is output.

Here, f _RF is the frequency of the output signal (RF signal), f _{LO / 2} is the frequency of the LO / 2 signal, f _IF is the frequency of the IF signal, and m and n are integers. As can be seen from equation (1), the output signal includes the IF signal (when m = 0) and its harmonics, and the LO / 2 signal (when n = 0) and its harmonics.

  However, as mentioned above, the output of the mixer circuit

の関係を満たす奇数高調波の周波数成分のみが出力され、

Only odd harmonic frequency components satisfying the relationship

の関係を満たす偶数高調波の周波数成分は抑制される（ｋは正の整数）。

The frequency components of even harmonics satisfying the relationship are suppressed (k is a positive integer).

When the mixer circuit shown in FIG. 16 is actually used, an RF signal having a frequency of m = 2 and n = 1, which has a relatively high conversion gain, is frequently used among output signals composed of a large number of frequency components. For this reason, the local oscillation signal input to the mixer circuit may be half the frequency of the LO signal to be transmitted.
Yozo Shoji, et al., "60GHz Band 64QAM / OFDM Terrestrial Digital Broadcasting Signal Transmission by Using Millimeter-Wave Self-Heterodyne System", IEEE TRANSACTIONSON BROADCASTING, VOL.47, pp.218-227, 2001. Yozo Soji and two others, “Proposal of Millimeter-Wave Self Heterodyne Communication System”, The Institute of Electronics, Information and Communication Engineers, IEICE Technical Report RCS2000-30, p. 1-8 Kenji Itoh, et al., "A 40GHz Band Monolithic Harmonic Mixer With An Antiparallel Diode Pair", IEEE MTT-S International Microwave Symposium Digest, pp.879-882, 1991.

  As described above, in the self-heterodyne communication system, it is desirable to satisfy the optimum condition of transmitting the RF signal and the LO signal with the same level of power. Further, in the receiving device of the self-heterodyne communication method, it is desirable that the power level of the received LO signal is as constant as possible.

  However, in the mixer circuit shown in FIG. 16, the LO signal (for example, m = 2, n = 0) having a frequency satisfying the above-described equation (3) is suppressed, so that the output power satisfying the optimum condition is reduced. However, there is a problem that a high power RF signal and LO signal cannot be obtained.

  Specifically, since the output power of the RF signal and the LO signal from the mixer circuit that satisfies the optimum condition is about −45 dBm, for example, in order to set the transmission power to 5 dBm, the power amplifier arranged at the subsequent stage of the mixer circuit The gain must be 50 dB. Since such a large gain cannot be obtained unless the power amplifier has a multi-stage configuration, the circuit scale becomes large and the transmission apparatus becomes expensive.

  The present invention has been made in order to solve the above-described problems of the prior art, and a self-heterodyne communication system in which a local oscillation signal and an RF signal can be obtained at the same level and with large power. An object of the present invention is to provide a mixer circuit suitable for use in the above.

In order to achieve the above object, a mixer circuit of the present invention is a mixer circuit used in a communication system for simultaneously transmitting an RF signal and an LO signal,
A first circuit having diode characteristics;
A second circuit connected in parallel with the first circuit, having impedance different from that of the first circuit and having a diode characteristic opposite to that of the first circuit;
It is the structure which has.

Here, the first circuit is
Having a first diode;
The second circuit includes:
A second diode having a junction area different from that of the first diode may be included.

The first circuit includes:
Having a first diode;
The second circuit includes:
Having a second diode;
At least one of the first circuit and the second circuit may have an impedance element,
The impedance element is
A transmission line or a resistor is desirable.

The first circuit includes:
A first diode and a first impedance element;
The second circuit includes:
A second impedance element different in impedance from the second diode and the first impedance element may be included;
The first impedance element and the second impedance element are:
It is desirable that the transmission lines have different characteristic impedances and have different line lengths, transmission lines having different characteristic impedances, or resistors.

The mixer circuit is
A first diode as the first circuit;
A second diode as the second circuit;
At least one of the first diode and the second diode may have a third diode having the same polarity and connected in series,
At least one of the first diode and the second diode may have a third diode having the same polarity and connected in parallel.

  Furthermore, a bias circuit for applying a predetermined bias voltage from at least one of the connection ends of the first circuit and the second circuit may be provided.

The mixer circuit receives a first signal and a second signal from one connection end of the first circuit and the second circuit, and the other of the first circuit and the second circuit. A third signal obtained by mixing the first signal and the second signal and a fourth signal that is a harmonic of the first signal are output from the connection end of
The power level of the third signal is
Desirably, the 1 dB gain compression point of the fourth signal is within the range of 1 dB gain compression point minus 13 dB,
More preferably, the output power levels of the third signal and the fourth signal are equal.

On the other hand, the wireless communication device of the present invention includes the mixer circuit,
A power amplifier for amplifying the third signal and the fourth signal;
It is the structure which has.

  In the mixer circuit configured as described above, the first circuit having the diode characteristics and the first circuit having impedance different from those of the first circuit and having the diode characteristics opposite in polarity to the first circuit are parallel to the first circuit. The second circuit connected to the first circuit and the second circuit have different amplitude values, and the phase difference is not 180 °.

  Therefore, since the suppression effect of the local oscillation signal provided in the conventional mixer circuit is reduced and the output power rises, the local oscillation signal and the RF can be selected by appropriately selecting the impedance values of the first circuit and the second circuit. The output power ratio of the signal can be adjusted. Therefore, the output power of the local oscillation signal and the RF signal can be set to the same level and larger than the conventional value.

  In addition, in the configuration in which at least one of the first circuit and the second circuit has an impedance element and a resistor is used as the impedance element, the voltage applied to the diode is substantially constant due to the self-bias effect. Become. Therefore, a decrease in the output power of the local oscillation signal at the time of high input power of the IF signal is suppressed.

  In the wireless communication device of the present invention, the first signal and the second signal are input from one connection end of the first circuit and the second circuit, and the other of the first circuit and the second circuit is input. The mixer circuit that outputs a third signal obtained by mixing the first signal and the second signal from the connection end and a fourth signal that is a harmonic of the first signal, the third signal, and the second signal Since the local oscillation signal and the RF signal having the same output power as that of the mixer circuit can be obtained from the mixer circuit, the gain of the power amplifier can be reduced. become. Therefore, a wireless communication device that operates stably at a low price can be obtained.

  Next, the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a circuit diagram showing the configuration of the first embodiment of the mixer circuit of the present invention.

  In the mixer circuit of the first embodiment, the anti-parallel diode portion is configured by pn junction type diodes D1 and D2, and the junction area S1 of the diode D1 and the junction area S2 of the diode D2 are different. Other configurations are the same as those of the conventional mixer circuit shown in FIG.

  That is, the mixer circuit of this embodiment includes an anti-parallel diode unit 1 having a diode D1 and a diode D2 having different junction areas, a short stub 2 inserted between the input terminal of the anti-parallel diode unit 1 and the ground potential, The parallel diode portion 1 has an open stub 3 having one end connected to the output end and the other end open.

  The short stub 2 is formed with a length equal to the electrical length of ½ wavelength of the LO signal, for example, the connection point 4 is opened by the LO / 2 signal and shorted by the LO signal that is the second harmonic signal. . Further, the open stub 3 has a length equal to the electrical length of 1/2 wavelength of the LO signal, for example, the connection point 5 is short-circuited by the LO / 2 signal and opened by the LO signal that is the second harmonic signal. It is formed.

  According to Non-Patent Document 3 described above, the conventional mixer circuit shown in FIG. 16 has an anti-parallel diode section composed of two diodes having the same characteristics, and therefore the LO / 2 signal and the IF signal have higher harmonics. The current flowing in the two diodes by the wave has the same amplitude and the phase is reversed. This suppresses the output of the second harmonic signal (LO signal) of the LO / 2 signal. In the mixer circuit of the present embodiment, the impedance values are made different by changing the junction area of the diode D1 and the diode D2.

  FIG. 2 is a graph showing the current-voltage characteristics of the mixer circuit when the junction area ratio S1 / S2 of the diodes D1 and D2 is, for example, 0.5.

  Referring to FIG. 2, when a forward voltage is applied (1.2 V) to a mixer circuit having a junction area ratio S1 / S2 of the diodes D1 and D2 of 0.5, the output current value is 14 mA. When a voltage is applied in the reverse direction (-1.2 V), the output current value is -8 mA. That is, it can be seen that the impedances of the diode D1 and the diode D2 can be set to different values by changing the junction area of the diodes D1 and D2. Thus, by changing the junction area of the diode D1 and the diode D2 so that the impedance values are different, the amplitude values of the current Id1 flowing through the diode D1 and the current Id2 flowing through the diode D2 are different, and the phase difference is also 180 °. Is not. Therefore, the effect of suppressing the LO signal provided in the conventional mixer circuit is reduced, and the output power of the LO signal is increased.

FIG. 3 shows simulation results of the LO signal output power P _LO (solid line A in the figure) and the RF signal output power P _RF (solid line B in the figure) with respect to the junction area ratio S1 / S2 of the diodes D1 and D2. Yes.

As shown in FIG. 3, in the mixer circuit of the present embodiment, the output power P _{LO of the} LO signal increases and the output power P _RF of the RF signal decreases as the junction area ratio S1 / S2 increases from “1”. . Therefore, the output power ratio of the LO signal and the RF signal can be adjusted by appropriately selecting the junction area ratio S1 / S2, so the output power of the LO signal and the RF signal is set to the same level and larger than the conventional value. it can.

FIG. 4 shows the measurement results of the LO signal output power P _LO (solid line C in the figure) and the RF signal output power P _RF (solid line D in the figure) with respect to the IF signal input power P _IF of the mixer circuit of this embodiment. (However, the junction area ratio S1 / S2 = 0.5). For comparison, FIG. 4 also plots the output power P _{LO of} a conventional LO signal (junction area ratio S1 / S2 = 1) (broken line E in the figure) and the output power P _{RF of} RF signal (broken line F in the figure). is doing. The measurement conditions are RF signal frequency f _RF = 60 GHz, LO signal frequency f _LO = 59 GHz, and LO / 2 signal output power P _{LO / 2} = 10 dBm.

As can be seen from FIG. 4, in the conventional mixer circuit, the value when the output power P _LO of the output power P _RF and LO signals of the RF signal is substantially equal to, was approximately -45 dBm. On the other hand, in the mixer circuit of this embodiment, it is about −23 dBm. Therefore, it was improved by about 22 dB compared with the conventional case.

Output power P _LO of the output power P _RF and LO signals of the RF signal from the mixer circuit as described above, the gain of the power amplifier larger is disposed downstream can be reduced. Therefore, if the mixer circuit of the present embodiment is used in a wireless communication apparatus, a local oscillation signal and an RF signal that are larger than the conventional and have the same output power can be obtained from the mixer circuit. Is possible. Therefore, a wireless communication device that operates stably at a low price can be obtained.

Since the output power P _LO of the LO signal increases as the junction area ratio S1 / S2 of the diodes D1 and D2 of the anti-parallel diode section 1 is decreased, the junction area ratio S1 / S2 is set to a smaller value for the above reason. It is preferable to do.

However, if the LO signal is made too large, it exceeds P1 dB (1 dB gain compression point) of the output power P _RF of the RF signal (see FIG. 5). Therefore, in the present embodiment, the junction area ratio S1 / S2 is selected so that the output power P _LO of the LO signal is equal to or less than P1 dB of the output power P _RF of the RF signal.

On the other hand, the most severe condition required for distortion of a transmission signal in recent years is to transmit at a power lower by 13 dB than P1 dB of the output power P _RF of the RF signal (13 dB Back off in FIG. 5). In this case, the output power P _LO of the LO signal is also limited to a transmission power that is 13 dB lower than P1 dB of the output power P _RF of the RF signal.

Therefore, in this embodiment, the output power P _LO of the LO signal from the mixer circuit is in the range of P1 dB to P1 dB-13 dB of the output power P _RF of the RF signal. The junction area ratio S1 / S2 is selected.

  In the present embodiment, the example in which the anti-parallel diode unit 1 is configured by the two diodes D1 and D2 has been described. However, the antiparallel diode unit 1 is parallel to and at least one of the diode D1 and the diode D2. Even in a configuration in which one or more diodes are connected in polarity, the same effect as in the case of changing the junction area ratio of the diodes D1 and D2 can be obtained if the number of diodes connected in parallel is different. In this case, if the total values of the junction areas on the diode D1 side and the diode D2 side are different, the individual junction areas of the diode D1, the diode D2, and the diodes connected in parallel may be the same or different. .

(Second Embodiment)
FIG. 6 is a circuit diagram showing a configuration of a second embodiment of the mixer circuit of the present invention, and FIG. 7 is a circuit diagram showing a configuration using a transmission line as the impedance element shown in FIG.

  As shown in FIG. 6, the mixer circuit of the second embodiment includes a first diode circuit 111 in which a diode D1 and a first impedance element 113 are connected in series as an anti-parallel diode unit 11, and a diode D2. And a second diode circuit 112 in which a second impedance element 114 is connected in series.

  The first diode circuit 111 and the second diode circuit 112 are connected in parallel so that each diode has a reverse polarity. Since other configurations are the same as those of the prior art, the description thereof is omitted.

  As shown in FIG. 7, in the mixer circuit of this embodiment, the first transmission line 115 is used as the first impedance element included in the first diode circuit 111, and the second impedance included in the second diode circuit 112. The second transmission line 116 is used as an element. The first transmission line 115 and the second transmission line 116 are formed with patterns having the same characteristic impedance and different line lengths, for example.

  As described above, by providing the first diode circuit 111 and the second diode circuit 112 with impedance elements, the impedances of the first diode circuit 111 and the second diode circuit 112 can be set to different values.

  Therefore, in the mixer circuit of the present embodiment, the output power of the LO signal and the RF signal is selected by appropriately selecting the lengths of the first transmission line 115 and the second transmission line 116, as in the first embodiment. Since the ratio can be adjusted, the output power of the LO signal and the RF signal can be set to the same level, and can be set to a larger value than the conventional one.

  Therefore, as in the first embodiment, when the mixer circuit of the present embodiment is used in a wireless communication apparatus, a local oscillation signal and an RF signal that are larger than the conventional and have similar output power can be obtained from the mixer circuit. Therefore, the gain of the power amplifier can be reduced. Therefore, a wireless communication device that operates stably at a low price can be obtained.

  In addition, since the first impedance element 113 and the second impedance element 114 are each configured by a transmission line, the impedances of the first diode circuit 111 and the second diode circuit 112 can be set to different values only by the wiring process. The number of parts and the manufacturing process are not increased, and the increase in the cost of the mixer circuit is suppressed.

FIG. 8 shows the LO signal output power P _LO (solid line G in the figure) and the RF signal output power P with respect to the transmission line length difference between the first transmission line and the second transmission line in the mixer circuit of this embodiment. It is a graph which shows the calculation result of _RF (solid line H in a figure) relation. In addition, the graph of FIG. 8 has shown the calculation result in case the characteristic of the diode D1 and the diode D2 is the same.

As shown in FIG. 8, in the mixer circuit of the present embodiment, the output power P _{LO of the} LO signal increases as the transmission line length difference increases. On the other hand, the output power P _RF of the RF signal slightly decreases as the transmission line length difference increases. Therefore, also in the mixer circuit of the second embodiment, the output power of the LO signal and the RF signal can be made substantially the same by appropriately selecting the line lengths of the first transmission line and the second transmission line. Can be adjusted to a larger value.

Also in this embodiment, similarly to the first embodiment, the output power P _LO of the LO signal from the mixer circuit is in the range of P1 dB to P1 dB-13 dB of the output power P _RF of the RF signal. In addition, it is desirable to select the impedance ratio between the first impedance element 113 and the second impedance element 114 of the anti-parallel diode unit 11.

  In this embodiment, the first diode circuit 111 and the second diode circuit 112 are each provided with an impedance element. However, the impedance element is the first diode circuit 111 or the second diode circuit 112. The structure which has in either one may be sufficient.

  In the present embodiment, the first impedance element 113 is connected in series to the diode D1, and the second impedance element 114 is connected in series to the diode D2. However, the first impedance element 113 is The diode D1 may be connected in parallel, and the second impedance element 114 may be connected in parallel with the diode D2.

  In this embodiment, a configuration using a transmission line as the impedance element is shown. However, a lumped constant element such as an inductor, a capacitor, or a resistor is used for the first impedance element 113 and the second impedance element 114. May be.

  Furthermore, in the present embodiment, the configuration using transmission lines having the same characteristic impedance and different line lengths as the impedance elements has been shown. However, transmission lines having the same line length may be used when the transmission lines have different characteristic impedances. .

(Third embodiment)
FIG. 9 is a circuit diagram showing the configuration of the third embodiment of the mixer circuit of the present invention.

In the mixer circuits of the first and second embodiments, a configuration of a mixer circuit is proposed in which the value is increased when the output power P _{RF of the RF} signal and the output power P _{LO of the} LO signal are substantially equal. Further, in the receiving device of the self-heterodyne communication method, it is desirable to make the power level of the LO signal as constant as possible as described above. Third embodiment, irrespective of the IF signal power proposes a mixer circuit was almost constant output power P _LO of the LO signal.

  As shown in FIG. 9, the mixer circuit of the third embodiment includes, as an anti-parallel diode unit 31, a first diode circuit 111 in which a diode D1 and a resistor 117 are connected in series, and a diode D2. The second diode circuit 112 is included. The first diode circuit 111 and the second diode circuit 112 are connected in parallel so that each diode has a reverse polarity. Since other configurations are the same as those of the second embodiment, the description thereof is omitted.

In the first diode circuit 111 of the present embodiment, by using the resistor 117 as the impedance element, the voltage applied to the diode D1 becomes substantially constant due to the self-bias effect. Therefore, in addition to the same effect as the mixer circuit of the second embodiment, reduction of the output power P _LO of the LO signal at high input power of the IF signal is suppressed.

FIG. 10 shows a measurement result of the output power P _LO of the LO signal with respect to the input power P _IF of the IF signal of the mixer circuit of the third embodiment. A solid line M in the figure indicates the measurement result of the present embodiment, and a wavy line N in the figure indicates the measurement result of the mixer circuit (corresponding to the first embodiment) to which no resistor is connected. The junction area ratio S1 / S2 between the diode D1 and the diode D2 is 0.5. The value of the resistor 117 connected in series to the diode D1 is 50Ω. The measurement conditions are RF signal frequency f _RF = 60 GHz, LO signal frequency f _LO = 59 GHz, and LO / 2 signal power P _{LO / 2} = 9 dBm.

As can be seen from FIG. 10, in the mixer circuit not connected to the resistor 117 (broken line N in the figure), the fluctuation in the output power P _LO of the LO signal was 1.1 dB. On the other hand, in the mixer circuit (solid line M in the figure) of this embodiment, it is 0.2 dB. Therefore, it was improved by about 1 dB.

  In FIG. 9, the first diode circuit 111 includes the resistor 117 connected in series with the diode D1, but the second diode circuit 112 includes a resistor connected in series with the diode D2. Each of the first diode circuit 111 and the second diode circuit 112 may have a resistor connected in series with the diode. In the configuration in which the first diode circuit 111 and the second diode circuit 112 have diodes and resistors, respectively, if the impedances of the first diode circuit 111 and the second diode circuit 112 can be set to different values, the first diode The junction area of D1 and the second diode D2 may be different or the same.

(Fourth embodiment)
FIG. 11 is a circuit diagram showing the configuration of the fourth embodiment of the mixer circuit of the present invention.

  The mixer circuit of the fourth embodiment has a configuration in which the forward rising voltage Vf1 of the diode D1 of the anti-parallel diode section 21 and the forward rising voltage Vf2 of the diode D2 are different. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  In this embodiment, in order to change the forward rising voltage Vf1 of the diode D1 and the forward rising voltage Vf2 of the diode D2, for example, Schottky diodes using metals having different work functions are used as the diodes D1 and D2.

FIG. 12 shows a simulation of the output power P _LO of the LO signal (solid line I in the figure) and the output power P _{RF of the} RF signal (solid line J in the figure) with respect to the forward rising voltage difference of the diode of the mixer circuit of this embodiment. Results are shown.

As shown in FIG. 12, in the mixer circuit of this embodiment, the output power P _LO of the LO signal increases as the forward voltage difference between the diodes D1 and D2 increases. On the other hand, the output power P _RF of the RF signal slightly decreases. Therefore, also in the configuration of the mixer circuit of the fourth embodiment, the first and first voltages can be selected by appropriately selecting the forward rising voltage Vf1 of the diode D1 and the forward rising voltage Vf2 of the diode D2 in the anti-parallel diode section 21. Similar to the second embodiment, the output power of the LO signal and the RF signal can be increased and adjusted to the same level.

  Therefore, similarly to the first and second embodiments, when the mixer circuit of this embodiment is used in a wireless communication device, a wireless communication device that operates stably at a low price can be obtained.

  Note that pn junction diodes may be used as the diodes D1 and D2. In that case, Vf1 and Vf2 may be changed by changing the impurity concentration of the P-type semiconductor or N-type semiconductor of the diodes D1 and D2, or by doping impurities having different energy levels.

  In the present embodiment, an example in which the anti-parallel diode unit is configured by two diodes D1 and D2 is shown. However, the antiparallel diode unit is in series and at the same polarity with respect to at least one of the diode D1 and the diode D2. Even in a configuration in which a plurality of diodes are connected, if the number of diodes connected in series is different, the same effect as that in the case of changing the forward rising voltage can be obtained. In this case, if the total values of the forward rising voltages on the diode D1 side and the diode D2 side are different, the individual forward rising voltages of the diode D1, the diode D2, and the respective diodes connected in series may be the same. It may be.

Also in this embodiment, similarly to the first embodiment, the output power P _LO of the LO signal from the mixer circuit is in the range of P1 dB to P1 dB-13 dB of the output power P _RF of the RF signal. In addition, it is desirable to select the forward rising voltage Vf1 of the diode D1 and the forward rising voltage Vf2 of the diode D2 of the anti-parallel diode section 21.

(Fifth embodiment)
FIG. 13 is a circuit diagram showing the configuration of the fifth embodiment of the mixer circuit of the present invention.

  The mixer circuit according to the fifth embodiment has a configuration in which a bias circuit 6 is added to the mixer circuits according to the first to fourth embodiments. FIG. 13 shows a configuration in which a bias circuit is added to the mixer circuit of the second embodiment, but the mixer circuit of the first embodiment or the mixer circuit of the third and fourth embodiments. The bias circuit may be added to the configuration.

  As shown in FIG. 13, the mixer circuit of the fifth embodiment includes a bias circuit 6 for applying a predetermined bias voltage to the antiparallel diode unit 11, and an output terminal of the antiparallel diode unit 11. The predetermined DC voltage is supplied from.

  The bias circuit 6 includes a DC voltage source 61 and an inductance element 62, and a DC voltage is supplied from the DC voltage source 61 to the antiparallel diode unit 11 via the inductance element 62. In such a configuration, the bias circuit 6 is opened by the inductance element 62 in the high frequency band.

FIG. 14 shows simulation results of the LO signal output power P _LO (solid line K in the figure) and the RF signal output power P _RF (solid line L in the figure) with respect to the bias voltage of the mixer circuit of this embodiment. The simulation was performed assuming a mixer circuit having the same configuration as that of the prior art in which the characteristics of the diodes D1 and D2 are equal and no impedance element is connected.

As shown in FIG. 14, in the mixer circuit of the present embodiment, the output power P _LO of the LO signal significantly increases as the bias voltage increases. On the other hand, the output power P _RF of the RF signal slightly decreases as the bias voltage increases. Therefore, also in the mixer circuit of the fifth embodiment, the output power of the LO signal and the RF signal can be increased and adjusted to the same level by appropriately selecting the bias voltage. Therefore, if the mixer circuit of this embodiment is used in a wireless communication device, a wireless communication device that operates stably at a low price can be obtained.

  Note that the mixer circuit of the present embodiment is configured to supply the bias voltage from the output terminal of the anti-parallel diode unit to which the open stub is connected, but the bias voltage may be supplied from the input terminal of the anti-parallel diode unit. Good. In this case, the short stub is shorted to the ground potential via the capacitor.

Also in this embodiment, similarly to the first embodiment, the output power P _LO of the LO signal from the mixer circuit is in the range of P1 dB to P1 dB-13 dB of the output power P _RF of the RF signal. In addition, it is desirable to select a bias voltage to be supplied to the anti-parallel diode unit.

1 is a circuit diagram showing a configuration of a first embodiment of a mixer circuit of the present invention. It is a graph which shows the electric current characteristic of the mixer circuit when the junction area ratio of two diodes of the anti-parallel diode part is 0.5. It is a graph which shows the simulation result of the output power of LO signal with respect to junction area ratio S1 / S2 of two diodes of an antiparallel diode part, and the output power of RF signal. It is a graph showing the output power P _RF of the measurement results of output power and RF signals LO signal to the input power of the IF signal of the mixer circuit shown in FIG. 3 is a graph showing a relationship between output power of an LO signal and an RF signal with respect to an IF signal indicating a range of output power of the mixer circuit shown in FIG. 1. It is a circuit diagram which shows the structure of 2nd Embodiment of the mixer circuit of this invention. It is a circuit diagram which shows the structure which used the transmission line as an impedance element shown in FIG. It is a graph which shows the calculation result of the output power of LO signal with respect to the transmission line length difference of the 1st transmission line shown in FIG. 7, and the 2nd transmission line, and the output power of RF signal. It is a circuit diagram which shows the structure of 3rd Embodiment of the mixer circuit of this invention. It is a graph which shows the measurement result of the output power of LO signal with respect to the input power of IF signal of the mixer circuit of 3rd Embodiment. It is a circuit diagram which shows the structure of 4th Embodiment of the mixer circuit of this invention. 12 is a graph showing simulation results of the output power of the LO signal and the output power of the RF signal with respect to the forward rising voltage difference of the diode of the mixer circuit shown in FIG. 11. It is a circuit diagram which shows the structure of 5th Embodiment of the mixer circuit of this invention. It is a graph which shows the simulation result of the output power of LO signal with respect to the bias voltage of the mixer circuit of 5th Embodiment, and the output power of RF signal. It is a schematic diagram which shows the structure of a self heterodyne communication system. It is a circuit diagram which shows the structure of the mixer circuit which has the conventional antiparallel diode part. FIG. 17 is a diagram illustrating characteristics of the mixer circuit illustrated in FIG. 16, in which (a) is a graph illustrating current-voltage characteristics, (b) is a waveform diagram illustrating an output waveform, and (c) is a waveform of an output signal; It is a graph which shows a frequency characteristic.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11, 21, 31 Antiparallel diode part 2 Short stub 3 Open stub 4, 5 Connection point 6 Bias circuit 61 DC voltage source 62 Inductance element 111 1st diode circuit 112 2nd diode circuit 113 1st impedance element 114 Second impedance element 115 First transmission line 116 Second transmission line 117 Resistor D1, D2 Diode

Claims (15)

A mixer circuit used in a communication method for simultaneously transmitting an RF signal and an LO signal,
A first circuit having diode characteristics;
A second circuit connected in parallel with the first circuit, having impedance different from that of the first circuit and having a diode characteristic opposite to that of the first circuit;
A mixer circuit. The first circuit includes:
Having a first diode;
The second circuit includes:
The mixer circuit according to claim 1, further comprising a second diode having a junction area different from that of the first diode. The first circuit includes:
Having a first diode;
The second circuit includes:
Having a second diode;
The mixer circuit according to claim 1, wherein an impedance element is provided in at least one of the first circuit and the second circuit. The impedance element is
4. The mixer circuit according to claim 3, wherein the mixer circuit is a transmission line. The impedance element is
4. The mixer circuit according to claim 3, wherein the mixer circuit is a resistor. The first circuit includes:
A first diode and a first impedance element;
The second circuit includes:
The mixer circuit according to claim 1, further comprising: a second diode and a second impedance element having an impedance different from that of the first impedance element. The first impedance element and the second impedance element are:
7. The mixer circuit according to claim 6, wherein the mixer circuits are transmission lines having equal characteristic impedance and different line lengths. The first impedance element and the second impedance element are:
The mixer circuit according to claim 6, wherein the mixer circuits are transmission lines having different characteristic impedances. The first impedance element and the second impedance element are:
The mixer circuit according to claim 6, wherein the mixer circuit is a resistor. The first circuit includes:
Having a first diode;
The second circuit includes:
Having a second diode;
Wherein among the first diode and a second diode, to at least one mixer circuit according to any one of claims 1 to 9 having a third diode connected in the same polarity, and in series. The first circuit includes:
Having a first diode;
The second circuit includes:
Having a second diode;
Wherein among the first diode and a second diode, to at least one mixer circuit according to any one of claims 1 to 9 having a third diode connected in the same polarity, and in parallel. The mixer circuit according to any one of claims 1 to 11 , further comprising a bias circuit for applying a predetermined bias voltage from at least one of connection ends of the first circuit and the second circuit. A first signal and a second signal are input from one connection end of the first circuit and the second circuit, and the first connection is input from the other connection end of the first circuit and the second circuit. A third signal obtained by mixing the second signal and the second signal and a fourth signal that is a harmonic of the first signal are output;
The power level of the third signal is
13. The mixer circuit according to claim 1, wherein the mixer circuit is within a range from a 1 dB gain compression point of the fourth signal to the 1 dB gain compression point− 13 dB. 14. The mixer circuit according to claim 13, wherein output power levels of the third signal and the fourth signal are equal. A mixer circuit according to claim 13 or 14 ,
A power amplifier for amplifying the third signal and the fourth signal;
A wireless communication device.

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